Radio testing apparatus



July 7, 1936. F. FAUSETT RADIO TESTING APPARATUS 5 Sheets-Sheet 1 VFiled Feb. 2, 1934 Nk Q avm E5 s: E9 4 22: 521 Ezmzo @U :Wu @/w n? n .SQNm. w 2@@@@@@@@ @mv .uh IFES m N H b m w WEG Q a. Q Q g Q N Q a wm. ,lA. SN i ,vom m. if g @52 2 6 5-2@ N ma@ w u @U N .f Q s@ :fr

July 7, 1936. F. FAUSETT RADIO TESTING APPARATUS Filed Feb. 2, 1954 3Sheets-Sheet 2 F. FAUSETT July 7, 1936.

RADIO TESTING APPARATUS 1934 3 Sheets-Sheet 3 Filed Feb. 2,

D.C.METER EEACTANCE l. 25 MFD.

D.c.vo Us /f 445 w rl M RESISTANCE E HO VOLTS Cal Patented July 7, 1936UNETED STAiES RADIO TESTING APPARATUS Miss.

Application February 2, 1934, Serial No. 709,516

17 Claims.

This invention relates to a portable testing instrument for radioapparatus and more particularly to a tester which incorporates a singleindicating meter for measuring all the electric units sought to bedetermined by apparatus of this type.

It is the object of this invention to provide a measuring instrumenthaving a comrnon scale for readings of both alternating current anddirect current units. Provision is made of a single direct currentmeasuring instrument in conjunction with a selector switch so that theformer may indicate direct current voltage and current values,alternating current voltages, capacities of condensers in microfarads,and resistance values in ohms. Furthermore, these electrical units maybe indicated in several ranges of the instrument; the embodimentdescribed hereinafter covers a total of twenty-five measuring ranges.

It is a further object of my invention to provide for the indication ofalternating current values switched into the circuit with the meter byusing a full wave rectifier system of the copperoxide or crystal type inconjunction with a DArsonval galvanometer coil. This assembly is sodesigned that variations in readings, occasioned by inherent changes inthe rectifier system, are minimized.

The invention also makes possible the convenient measuring ofalternating or direct current components of composite potentials, to theexclusion of each other.

It is a further object of my invention to so' arrange the meteringinstrument in conjunction with a series of tube sockets, in jacks and aselector switch that a series of measurements normally attendant thetesting of a radio receiver or analogous apparatus may be made by aserviceman with the least expenditure of time and effort.

Other objects and purposes will appear from a more detailed descriptionof my invention taken in conjunction with the drawings, in which Fig. 1is a plan view of the panel of the testing apparatus,

Fig. 2 is a circuit diagram thereof showing the elements upon thereverse side of the panel,

Fig. 3 a siinplied showing of the metering arrangement for measuringdirect current values,

Fig. 4 is a simpliiied circuit diagram showing the connections fordetermining resistance values,

Fig. 5 is a simplified diagram showing the arrangement whereby directcurrent and alternating current voltages may be read upon a single scaleupon the meter, and furthermore whereby capacities may be determined,

Fig. 6 is a vector diagram of the metering circuit when alternatingcurrent voltages are measured, and

Fig. 7 is a simplified showing of the connections between the socketsshown in Fig. 2 and the pin (Cl. Z50-20) jacks provided on the panelwith the switches associated with several of them.

The single indicating instrument is calibrated to function as amulti-range direct current milliammeter, a multi-range ohmmeter, amulti-range direct current voltmeter, a multi-range alternating currentvoltmeter, and a direct reading capacity meter. 'Ihe meter, consistingof a DArsonval galvanorneter movement having a full scale sensitivity ofone milliampere (0.001 amp.) andadjusted for an eii'ective internalresistance value of 300 ohms, is selectively switched into the desiredmeasuring circuits by the operation of a Z-gang li-position rotaryswitch.

Multi-range meters for measuring direct current voltages and currentsare old. Furthermore, a meter for measuring alternating current unitsand direct current units with a common uniformly calibrated scale isalso known. 'I'he latter arrangement involves the use of a rectifyingsystem for rectifying the alternating current energy before it ismeasured by a DArsonval movement with which the rectifying system isconnected. The provision of a rectifier results in readings which varyunder several conditions, since it is an inherent characteristic of suchrectiers to change in resistance with changes in current density,temperature, frequency, and age. The instant invention minimizes thesevariations as explained hereinafter. Y

Alternating current values, when measured by conventional alternatingcurrent instruments, are not indicated as having the same values whenrectied and measured with a DArsonval galvanometer movement. This is sobecause the former type of instruments measures root mean square oreiiective values of the alternating current energy, whereas theDArsonval galvanometer indicates the average values. In the case ofdirect currents, the average and the effective values are the same. Inthe case of alternating currents, the average value bears a relationshipof 1 to 1.11 to the root mean square or eiective value. Thus, ii analternating current potential of 100 volts, as measured by analternating current voltmeter, is applied to a rectifier andsubsequently indicated upon a direct current instrument7 the same reads90 volts. For that reason, the average Value of 90 volts must bemultiplied by 1.11 in order to obtain the correct Ialternating currentrreading. 1

The form factor of 1.11 is calculated for sine waves, which wave form isapproximated in commercial practice.

Although resistance means have been utilized previously for adjustingthe sensitivity of the direct current meter to differentiate betweenalternating current and direct current energy, the instant inventioncontemplates the use of capacitive reactance to eiiect the necessaryadjustment with many attendant advantages. The instant inventioncontemplates the use of one or more condensers which have the effect ofproportioning to the proper degree the total impedance of the circuitsfor. measuring alternating current values compared to those employed formeasuring direct current Values, so that Ymore current is permitted topass throughY the DArsonval coil in the rst case than in the lattercase.v 'Ihe form factor 1.11 may be modified by a suitable selectionVofV the condensers in order to? adaptthe Y metering arrangement tovarying conditions.

' In Va universal tester of this type embodyingY a singlemeter,consideration must be' given to the'V Vcurrent density characteristic ofthe rectifier Y amount, the resistance of theV rectifier'may in'- whichis associated with the'meter. VT'his characteristic manifests itself inthe form of an increase in rectifier resistance corresponding to aVdecrease in the electricalv load. vNo two instru- -ment rectifiers haveYexactlythe same current density characteristics,V but' the Yaverageresistance may be assumed to amount to 5'00ohms with a'load of 1milliampere. With'a load of half this crease as much as 50%. Thisaccounts Aforthe irregularities inthe amount of deflection in in- Ystruments of Vthis type. The current density characteristic may bebetter understood bya tab- Y Yul'ation Yof resistance valuescorresponding to `cur'- rent values, based on a typical rectifier unitwhich has an internalv resistance value of 500'ohms,.withV a Yload of 1Vmilliampere, as follows:

Milliamperes .Y VOhms The eiect of the Ycurrent densityrcharacteristicsis reduced, however,by the usual' multiplier resistors as usedin-alternating current voltmeters of the rectifier type. For example,assuming that a rectifier having the above-tabulated resistance valuesis used with amultiplier resistor fora 5- Y volt measuring rangegwith ameterrsuch as that described herein;Y a'total vcircuit resistance VofVi500V half-scale deflection The effect'isstill further Y redueedwhenthe range ofthe meter is extended to 25 volts, with a multipliervresistor added forY increasing the' total resistance to a value of22,250

ohms. In this case, the eiTect upon the total resistance is obtained bydividing 260V ohms, which is the increase Yin resistance at half -scaledeection, by 22,2530 ohms, Yan increase of Y1.15%.V

In accordance With/the instant invention, the

effect' of the current density characteristic of the instrumentrectifier is further minimized by using a series capacitor for the lowrange as Ya multiplier reactance; instead of utilizing a multiplierresistor. This arrangement forms an impedance circuit'wherein thecapacitive reactance is about d minedl by dividing 5,000 by 3890.

Y amounted to 5.8% of the total resistance.

2,046,450 Y .Y y degrees out ofV phase with the meter andrectifier-resistance, so'that the impedance elements may be representedby a right-angled triangle in which theresi'stance of the Vcircuit isrepresented by av short leg of the triangle and the capacitive reactanceby a long leg. The resulting impedance is, of course, represented by thehypotenuse of the triangle.

is shown as a value of 800 ohms, obtained by adding the resistance ofthe meter to the resistanceV of two legs of the rectier unit with afull-scale deflection load ofA one milliampere; The capacitive reactanceis shown as having a value of 3800 ohms, which isthe reactanceof a 0.7Vmfd. capacitor for'a frequency of 60 cyclesrper second. The resultingimpedance is 3890 ohms, as-determined bythe solution of theY impedanceformula y2:,/122445 X62 Y The above values are characteristic of a..typically constructed analyzer so that the form factor of therectierunit is about 1.29 in'this case, deter- As may beV seen in Fig. 6,slightvariations in the length of that side of the triangle which rep- Yresents thel resistance have comparatively little effect on the' lengthof the hypOtenuse, whereas ThisV condition is graphicallyi representedin Figure 6, in whichV the resistance Y the: variations of the rectifierresistance would be Y Vconsiderable if the elements of the circuitimpedance were additive algebraically rather than vectorially, that is,if these variationswere capable of being represented by a straight lineinstead'of by a triangle such ,asY that' described. VIt was shown labovethat .the increase in the total resistance of a, 5-volt circuit athalf-scale Vdeiiection,

by reason of they current density characteristic',

When a 4500-0hm multiplier resistor is employed, With the arrangementaccording to the instant invention, an increase of 260 ohms of theresistance leg of the triangle increases the length 0I the hypotenuseVonly 50 ohms, so that the increaseY inthe impedance amounts to less thanVor V1.3% as compared to van increase of 5.87%

when a multiplier capacitor is not used. In other words, by using-acapacitor Vas a multiplier reactor instead of using amultiplier resistorfor the Vlow range of the alternating current measuring functions of themeter, Ythe voltage indications are made to conform very closely to auniform scale distribution for Vpractically all measuring requirements,as the variations inthe resistance Y 0f the rectifier unit are made` tohave comparatively little eflect in the circuit in which the impedanceis composed mostly of capacitive reactarice.Y Y Y Of lesser importanceis the effect of aniblent temperature variations on the internalresistance of instrument rectiers, in which decreasing temperaturescause increasing resistance Values. TheV reactance elementrof theYarrangement according Vto the invention reduces these errors toYnegligible proportions `by the same principles which operate to reducethe Veffect of the current density characteristic. Y Y Y Y Likewise, anyvariations in the resistance of the rectifier,`measured by the agingthereof, or by changing of the frequency of the alternating currentimposed thereon, exercisera, minimum eiTect s upon the reading which isobtained.

The adjustment of the 5-volt alternating current range of the tester isaccomplished by inserting a condenser C1 of suitable capacity in serieswith the rectifier I2 and meter II so that the meter needle assumes thefull-scale position with an applied alternating current potential of 5Volts. Subsequent to the adjustment of the 5- Vclt range for alternatingcurrent potentials, the higher ranges are similarly adjusted byinserting condensers Cz-C of suitable capacity across the severalmultiplying resistors, which serve to bypass more current through themeter when measuring alternating current values than when the sameterminals are used for measuring direct current values. The eXactadjustment of the alternating current measuring circuits may be made aswell by means of one or more variable resistors in series with thecondensers, insteadl of by adjusting exactly the condenser values. Thevectorial representations for the higher indicating ranges of the meterare additional triangles, as shown in 6, appended to the oneV shown inthis iigure, in which the resulting impedance suitably affects thepassage of current through the rectifier and measuring instrument. Thesecapacities are given in the table following hereinafter.

The means employed for obtaining a uniform scale distribution foralternating current indications as described above are found to beaccurate within 5% of full-scale values which is generally accepted asbeing sufficient for all practical purposes, since practically allmeasurements required in radio servicing involve direct currentpotential values. As a matter of fact, alternating current power supplypotentials usually have a permissible Variation of 10% and thisvariation is reflected in the alternating current filament potentialvalues by the same ratio. Most radio power pack rectifier circuits areof the fullwave type, and the alternating current plate potentials canbe compared with each other for the purpose of determining whether ornot an unbalanced transformer winding exists without the necessity of anaccurate measurement of these potentials. Output measurements may bearb-itrarily adjusted in practice for maximum indications, and accuratemeasurements in electrical terms are not always required. Practicallyall other measurements involve direct current values in the measurementof which the crystalline rectiiier unit of the tester is not employed.

1n View of the fact that the reactance of a capacitor is a function ofthe frequency of the alternating current energy applied thereto, it isnecessary that the condensers be calibrated for a predeterminedfrequency which is likely to be encountered by the serviceman. Thus thecondensers shown in the drawings, in Figs. 2 and 5, have the followingvalues corresponding to the most universal commercial frequencies:

Fw Capacity in Mfds.

quency in cycles pgnsc C1 Cz Ca C4 Ct Cu Y (i0. 0. 7 0. 08 0. 015 0. 0150. 006 0. 002 50 0. 84 0. 096 0. 018 0. 018 0. 0072 0. 0024 42. 1. 0 0.114 0. 021 0. 021 0. 0086 0. 0029 30 l. 4 0. 1G 0. 03 0. 03 O. 012 0.004 25 1. 68 0. 192 0. 036 0. 036 0. 0144 0. 0048 The variations infrequency1 normally encountered in commercial practice do not materiallyaffect the accuracy of the instrument for the reason that thesevariations are sma11. The practicability of synchronous electric clockswhichA depend for their operation upon the maintenance of asubstantially constant frequency is an established fact.

A simplified diagram of the arrangement for effecting an adjustment ofthe sensitivity Vbe-` tween the reading of alternating current anddirect current voltages is shown in Fig. 5. Herein, when direct currentvoltages are applied to the tester within a range of5 volts, the meterhaving an effective internal resistance of 300 ohms is connected inseries with a resistance of 4700 ohms to obtain a maximum deflection at5 vo-lts, representing a 1,000 ohms per volt sensitivity. At higherranges of applied voltages, the multiplier resistances are inserted inseries to the several pin jacks, in which case the instrument may beconnected for a. maximum deiiection for any desired range. Theseresistances havevthe following values in order to carry throughthe 1,000ohms per volt relationship. A resistance of 20,000 ohms is added for'the25 volt terminal, 100,000 ohms for the 125 volt terminal, 125,000 ohmsfo-rthe 250 volt terminal, 250,000 o-hms for the 500 volts terminal, and750,000 ohms for thev 1250 volt terminal. The condenser Cr serves toblock the direct current potentials from the rectifier. The meter doesynot register alternating current values when the switch i4 is set fordirect current measurements because the rectifier unit is not in themetering circuit. Thereby it is possible to measure direct currentcomponents of composite potentials to the exclusion of alternatingcurrent components. When the switch I4 is set `for alternatingmeasurements, the componente of the latter in composite potentials aremeasured to the exclusion of direct current components on account of theblo-cking condenser l2. The relation of the reactance of the condenserC1 of 0.7 mid. capacity in the rectifier circuit was explained above. Inthe example chosen, this reactanceamounts to 3800 ohms, giving thedesired full-scale deflection upon the meter when an alternating currentvoltage bearing an effectivevalue of 5 volts is connected between thecommon Yand 5 volt terminals. The condensers Cz-Cs shunting themultiplier resistors affect the combined impedance of these' elements ina .diminishing sense to that effective alternating current values may beproperly indicated on the` same scale as the direct current values.

The invention also enables a convenient measurement of the capacities ofcondensers in three different ranges upon a uniform scale of the meter.For this purpose an ordinaryV 11G-volt power supply, in series with thecondenserof unknown value, is connected in the circuit of the rectifierand its associated condenser together with a proper value of shuntingresistance. A fuse is provided for protecting the meter and flo shuntsagainst such overloads as might be ocl casioned by an inadvertentattempt to measure the capacity of a short-circuited condenser.

A self-contained 41/2 volt battery in .the tester cabinet makes possiblethe measurement of resistance values for several ranges. of 1,000,10,000, and 100,000 ohms may beread upon the same ohms scale Yuponthe'multiplicati'on of the proper decimal factor. A variable shuntresistor is provided for adjusting the ohmmeter circuit for Yan accuratereading of the zeroohms value. A l5-volt source of potential Ymay beconnected to the tester to obtain afmegohm rangeof the meten i Theseranges v'The above design features are incorporated in ahandy andcompact portable tester,V the panel of Whi'chfisY illustrated in Fig. 1,and the circuit diagram of which is shown Yin Fig.` 2.

The multiple functions oifthemas Il .are

' controlled by the setting of the 4'-,position, '2- gang rotary switchI4 having two arms 35 and 36 connected to thepositive and negativeterminals e vl5 and |6. of. the meter Vby'conductors 45 and V46,

respectively. These arms 35 and 36smay be set at the D. C. M. A.position `to have the meter Vfunction as a direct current'milliammeter,at the f A. C. V.-Mfds. position for lthe meter to function Y' Vas `analternating eurent voltmeter and a capacity meter, at` the D; C. Yvoltsposition Vto Vhave the meter function asV a direct current voltmeter,and

Vat the-ohms position'tohave the meter function Vas an ohmrneter.VariousY ranges ofthe meter operating as a direct current or alternatingcurrent voltmeter may berselected by a'series of pin '3 jacks 43 on theright side of thepanel cooperat- Y ing with a common pin jack 42. Themeter may be employedfor ranges of 5, 25,7125, 250, 50),.and

i 1250 volts.V The values of the multiplier resistors `24 toobtain theseranges at a sensitivity of v1,0001ohms per volt are given above. Severalranges of the instrument operatingzas'V aVV milli-Y ammeter may beselected by one of a series of pin jacks 33 :at the left side of thepanel co-operating with the Vcommon terminal YpinY jack 32. The

V,shunt resistors 26'-3|, *toV obtain the operating ranges of theammeter at V1250V '500, 2750, 125, 275,

, and 5 milliamperes, have the following *values- Y Resistor 26 has avalue of 0.3 ohms; 21, 0.45 ohms;

28, 0.75 ohms;'29, 1.5'ohms;Y 30,712 ohms; and 3|, ohms. These shuntsco-operate with the resistance Yof the metering circuit which is ad-Vjusted to eXactlyYBOO vohms by the insertion of'a resistor I8 having avalue equal Vto the difference between'the resistance of the meter and300 ohms.

Several ranges of capacityV may be measured by the meter by suitablyemploying a common terminal |1| atrthe top of the panel in selectivecooperation with pin jacks V|14, |15, and |16. ,The measuring circuitforcapacity readings is controlledby the. depression `of a push buttonswitch `minal pin jack |34k with terminals |35, |36, |31,

|38 and |39, as explained hereinafter. A variable resistance |3|isicontrolled by the ohmmeter adjuster |30V to make suitablecompensation for th ,Y varying potential of the battery.VVV

Y into the tester at the pin jacks 50 to V51.

' '(Fign l) 4, 5, |5,.1,.T.VC.,Y l, 2, and 3. This nu Vmericaldesignation Vcorresponds to the standard lFor-"the purpose ofVpresenting the potentials present in a radio set to thertester, ananalyzing plug P, adapted to co-operate With proper adapt- Y ers, isconnected atY the end of the cable A leading from thetester.

The terminals of the plug or adapter, connected-With a series ofconductors in the cable, bring the potentials ofthe receiver The cableYconductors terminate Vat the pin jacks, whichare labeled on the panelfrom left toright practice recently adopted fornumerically designatingthe tube and socket terminals. Numeral signifies the grid terminalnearest the conven- Ytional plate terminal which is designated 2.Y

Numerals 3 and 4 designate the-filament or heater |66"and |61 extendfrom pin jacks'l, 62, 65, 66, and 61 to the terminals of the sockets 49,59,

Y associated with the meter, make possible a highly terminals on alltypes of tubes regardless of the number of terminals. The conventionalcathode terminal is represented by numeral 5. The terminals lnumbered 6and 1 are applicable to tubes which Vhave more thanV five baseterminals. The 5 Y Vconventional control grid terminal s designated asthe Top cap and abbreviated T. C. and is so designated on the panel.YThe T. C. pin jack 5|).

o on the. panel is connected directly through the analyzingV cable Atothe'rlug VL which terminates 10Y the short flexible insulated conductorat` the top of the analyzingplug P. It is preferable to have Y VthisVlug L Yconnected through a flexible lead soV that connections may bemade more convenient'- `1y, which at times isV dimcun; when the lug is15;

rigidly'attached to the analyzing plug. Jumpers or wire connectionsextend between pin jacks 50, 5|, 52, 55,56, and 51 and pin jacks 60, 6|,62, 65, 66 and 61, eachof which may be broken by depressing Y itsVYcorresponding push Y button switch 10, 1|, 12,15, 16, and 11.

Four sockets, 49,` 59, 69, and 19 are providedV on the analyzer panelfor accomodating tubes having four, five, six orseven prong elements inthe base The'rsockets have their receptacles numbered in accordance withthe standard designationjexplained above. A pin jack is provided on. theanalyzer panel Vinto which one end of `a suitable conductor may beinserted, the opposite` end having a proper clip for engaging the Topcap of .a tube inserted inv any one of the tube sockets on the Vanalyzerpanel. The Top cap pin Yjack is connected to the'pinjack 60 by conductor|60. Likewise conductors I6I, |62, |65,`

69,and 19, designated 2,5,-6, and-1,or to as many of those terminalsasthe sockets have.V

Y Conductors |53 and |54 extend from pinV jacks 53 yand 54 directly. tothe 3-and 4 terminals vof the several tube sockets. In view ofthe factthat these terminals invariably ycarry the heater-or filament current,no switching means is provided for breaking the circuit of theseconductors, since the potential acrossY them is the only reading thatdesired,V The arrangement of the pin jacks associated Vwith theVconductors of the analying cable, in Yconjunction vv'lth the particularswitching means Yand the several pin jacks flexible system oftesting'operations.V these operations are outlined below.V

Measurement of'plat'e current Some of In view of the fact that theVplate current 'ofV a Vtube isV the result of practically all oftheelec`V trical factors involved inthe circuits leading to the tube,anormal v*plate current value is fairly `conclusive evidence'that thecircuits leading'to VVplate current reading is observed. VIn order rtoVmeasure plate currentsV with the tester disclosed Y herein, the testerpanel is cleared and the radio re" 70A Vceiver which is being testedconnected for nor-V mal operation. While the radio is de-energized,

' the tube from the stage ofthe receiver under test is removed andis'placed in one of the sockets, 49,

59, 69 or 19 in the analyzer panel, depending upon 75 Y' tween the pinjack 32 and the pin jack 62. Anv other test probe conductor is connectedbetween pin jack 52 and the pin jack 33 for the 250 milliampere range.The plate current is observed upon the momentary depression of pushbutton 12.

In the above test, the instrument il, operating as a direct currentmilliammeter, is inserted in the cable conducting the plate currentbetween terminals 52 and 62. The jumper between these two terminalsnormally carries the plate current and the depression of switch 12breaks the normal circuit and allows the circuit containing the meter toconduct the plate current between terminals 52 and 62 to measure thesame. It is usually advisable to first observe the plate currentreadings on the 250-milliampere range, after which the connector may beshifted to a suitable lower range. The metering circuit in itssimplified form is shown in Fig. 3. The above procedure may becontinued, without changing the connections, from tube to tube until theplate current measurements have been made for all of the tubes in theradio; or until a tube is encountered in which there is an indication ofan incorrect plate current value, in which case the operator shouldundertake a more detailed analysis in an effort to isolate the cause ofthe incorrect plate current condition by potential and resistancemeasurements as outlined hereinafter.

Tube testing When a radio receiver is in proper operating condition, theuse of an analyzer for testing the tubes in the radio tube socketsprovides a method of testing tubes which is unexcelled by any tubetester for practical purposes in the detection of weak or noisy tubes.This preliminary test of a tube is performed by placing the tube in theanalyzer socket and tapping or thumping it while it is held away fromthe radio receiver. Thereby, any rattling or rasping noises occasionedby the tapping action which characterizes a faulty tube may bedefinitely attributed to the tube rather than to the noises occasionedby some loose part in the radio chassis. It is of course understood thatthe analyzer P is utilized to bring the potentials from the radioreceiver socket to the tube under test on the analyzer panel.

'Iube test readings of amplifier tubes are obtainable as a logical stepfollowing the measuring of plate current, as described above, by theconnection of the self-contained l1/2 volt battery B in the tester tothe pair of pin jack terminals which corresponds to the input grid ofthe tube under test. In the types 26 and 21 tubes, in which the Iterminal corresponds to the input grid as explained above, the followingtesting procedure is carried out: The normal plate current is rstobserved by the depression of push button switch 12. A flexibleconnector is extended from pin jack |34 to 5l. Another connector isextended from the pin jack 136 to 6l. These connections serve to placethe positive terminal of the battery Bnearer to the grid upon thedepression of push button switch 1l so that, upon the simultaneousdepression of switch 12, a change in the reading of plate current isnoted in an increasing sense. It is possible for the connections to bereversed so that the negative terminal of the battery is placed nearerthergrid and, at the simultaneous depression of switches 1l and 12, adecrease of plate current is noted.

In the types 2li and 25 tubes, the input grid is connected to the Topcap terminal, and the battery is connected'to "I. C. pin jacks 5t andSil instead of to the l pin jacks 5l and 6l. The tube test is thenobtained by depressing push button switches 1li and'12. Finally, theterminals 6 and 1 may represent the input grids of any other types oftubes, reliance being had upon radio service notes for this informationin order to perform the desired tests. The multiplier and shuntresistors of the ohmmeter prevent the short circuiting of the batterybefore the depression of the corresponding input grid push buttonswitch. The amount of increase or decrease in the plate currentindicates the extent to which the input controls the plate currentoutput, which in turn corresponds to the amplifying ability of the tube.After a certain amount of experience the operator is capable of judgingthe fitness of the tubes, as is evidenced by the above test.

Another method of testing tubes in a" radio receiver is provided by themeasurement ofthe output of the receiver, as explained hereinafter. Thereplacement of faulty tubes effects-an increase in the output energy ofthe receiver.

Potential measurements After proceeding with the preliminary steps orplate current measurements and tube testmg until a tube socket isencountered in which the tube is passing incorrect plate current, and inwhich the replacement of the tube does not correct this condition, it isnecessary to resort to more specific tests for the purpose of isolatingthe circuit which is defective. To do this, the analyzer panel iscleared and the switch I@ is set at its D. C. volts position. A testprobe conductor is connected between the pin jack i2 and one of the pinjacks correspon-ding to the cathode terminal of the tube circuit. In thecase of tubes having indirectly heated cathodes, the cathode terminal 5is connected with pin jack 55 or 55. In the case of lamentary cathodes,the connection of the test probe connector is made to either pin jack'53or 54. Another test probe connector is connected to one of the pin jacks43depending upon the range desired, and the free end thereof isselectively applied tothe pin jacks 55.5 to 51 in order to measure thepotentials applied to the tube with respect to the cathode terminal Themetering circuit in its simplified form is shown in Fig. 5. Upon thefinding of a defective circuit by comparison of the potential readingsnoted with those published by the manufacturers of the radio receiver,the ohmmeter is utilized for locating the defective part, as explainedhereinafter. After the Vpotentials are noted, it is advisable todischarge the condenser C1 through the multiplier resistors bymomentarily touching the free contact ends of the test lead conductorstogether before disconnecting the other ends of theV leads from the pinjacks for the purpose of measuring the potentials' be- Ytween theelectron-emitting terminal andthe other terminals of the tube,"` it ispossible Y. to quickly determine thepotentials existing between otherterminals by using any terminal other than Ythe cathode or lamentas thereference point. The Idesign ofthe tester disclosed herein with thevarrangements of the pin jacks thereonV results Vin `what has vbeentermed affree reference point tentials therebetween and the Vremaining`tube terminals quickly determined by plugging connectors between thecorresponding pin jacks Yand the terminals appurtenant the desired rangeof the meter'.Y The radio chassis, the cathode, the` iilament, or anyelementof a tube circuit regardless of the terminal .arrangement of` thetube may be used as the reference point for potential Y Y resistancereading on the meter, these ends are and resistance tests.Y Y Y Y YThe'principles of the"free'ref erence'polntsystem of analysis through ananalyzing cable may be compared to the principles of the modern'tele-Vphone switchboardV through kwhich vany subscriber maybe connected withany other subscriber, and

- Vwhich isv easily adaptable to changes-in the list or subscribers. Inthis analogy,V the tube Vterminals correspond to the subscribers. Thetester; accordingrto Vthe instant invention is, fundamen-Y tally,'aminiature switchboard with an analyzing plug and cablefor extending allof the circuits YVof a radio tube socket to conveniently locatedpin jackterminals toiwhich any range of .the meter may be applied for anydesired current, potential i This arrangement provides access topractically every circuit in a Y or resistance measurement.

' radio," without dismantling the radio chassis. f This designfurthermore renders the tester particularlyadaptable'to new testingprocedures and precludes possibilities of obsolescence. t v

In the course of taking potential measurements for filament circuitssupplied by alternating curbetween the pin jacks 42 andf53 and another[one between one of the pin jacks 43 of Vsuitable position. A test probeconductor isY connected Resistance analyses For general radio analyses,it is recommended that the plate current indications be relied upon ashaving primary importance, because correct plate current values almostinvariably indicate Y correct potentials' applied to the tube sockets;

analysis in which the plate current fluctuates `or1is radically loworhigh, it 'is' then advisable to con- Y. '60" Whenever a socket isencountered during a general centrate Ythe investigationY at that socketin an effort to determine the cause ofthe radicalplateV current. Thisinvestigation may lead'to the use of Vthe ohrnmeter functionsvof theanalyzer for .pointto-point tests ofthe component elements of thecircuits Yof the; socket. Before undertaking Vsuch Y tests, the radiomust be disconnected from theV power supply outlet. The Yresistanceanalyses may be made between the pin jack terminals of the analyzercable circuits, or from these ter minals to the chassis or otherreference points, without removing the analyzing plug from the Vsocketin which the circuit defect apparently exlieu-of the usual current andpotentialanaylses because some types of resistors change in re-`sistancevalues when operating under'their nor.- mal loads. Furthermore,it is generally advisable z to Vdisconnect resistors from parallelcircuits k,in

order to testthem, whereas Vcurrent and potential values canbe analyzedwithout disturbing nor mally permament connections. V Y

The instrument I is connected for 'its function as an ohmmeter as'shownin Fig. 4 bythe setting.v

of the switch I4 tothe Ohms position. A test connector .is'inserted inthe common pin jack |34 and another one is inserted, in one of the pinVjacks |35., |36 or |31; depending upon theY range of the ohmicmeasurements desired. The latter three. pin jacks correspond to rangesof 1,000,V 10,000, and 100,000 ohms respectively. Be-` fore connectingthe resistanceof unknownvaluei between the ends Vof the connectors toobtain the contactedcorresponding to zero ohmsrand the knob |30ofV therheostat |3| is turned until that .Y

value Vis indicated Von the meter, deflection of the needle. Y Y Y Inorder to readY resistance valuesV upV tojlY megohm, provision is madefor the connection of by a maximum a 45-vo1t source of `potential in themeasuring cir-V cuit. The positive terminal'ofa 45-volt battery isconnected to kpin jack |38 andV one end of La test lead conductor isconnected tothe negative ter- Y Yminal thereof. Another test leadconductorls The ohmmeterV circuit is adjusted for zero ohms bycontacting the connected to the pin jack |39.

free ends ofthe test lead Yconductors and rotating the ohmmeter rheostatv|307-t0 obtain Vmaximum deflection of the meter. The vvalue of anunknown resistor connected between the `freeends j of the conductor Vwinbe indicated on the ohms scale of the meter by multiplying the readingbyV The resistors associated withftheohmmeter circuit'have the followingvalues.. /Resistor V|3|-is adjustable between the limits of 0 and 3600ohms; Resistor has avalue Vof 1600- ohms; ||8,. 33

ohms; |22, 3269 ohms; and |23, 31500 ohms.-

YThe resistance values of circuit portions may be Ydetermined by theohmmeter upon the proper connections of Ythe ohmmeter terminals 'be-,j

tween the several circuit elements. Y Capacitor leakage tests i Whilethe higher ranges ofthe ohmmeter may Y leakage tests. The RadioManufacturers Association recommends that the insulation resistance ofxed paper, capacitors should not be less than 500 Vmegohrn microfarads',at a capacitor temperature of 68 F., the test being made by applying a Ydirect current 'potential of 250 volts Yto la corn-l pletely dischargedcapacitor and maintainingtlsf potential for three minutes before. theinsulation generally -be sufliciently approximatedin practical servicevprocedure .by employing a 25o-volt direct current potential inseriesVwith the 250-vo'lt direct current range 'of the meter When va testingdevice for supplying a'250-voltdirect current potential isznotavailable, vtheplatepotential Vresistance is measured. 'These`conditions can "ZuV of the" output tube of a radio receiver maybeutilized by making the following connections. The analyzing plug P isinserted in place of one of the power output tubes in the receiver andthe displaced tube is mounted in the proper socket in the analyzer. Theswitch yI4 is set at its direct current Volts position. A conductor isconnected between pin jack 42 and the pin jack corresponding to thecathode, which is 53 in the case of a 4-pin type of tube or 55 if thetube is of the 5-pin type. One end of another conductor is connected tothe Z50-range pin jack d3, the other end of which is designed to beapplied to the capacitor. One end of another conductor is connected tothe plate terminal of the power tube at either pin jack 52 or B2, andits other end is free for application to the capacitor. A direct currentpotential of approximately 250 volts now exists between the free ends ofthe conductors and, upon application thereof to the capacitor,.anindication of its condition is obtained. A good capacitor takes a chargethrough the meter which will be indicated by a maximum reading at theinstant the connection is made, with the reading decreasing to zero asthe charge is completed. IThe instantaneous maximum reading Varies withthe capacities of the condensers under test. A condenser with aresistance leakage is indicated by the failure of the meter needle tocomplete its traverse to the zero position. The failure of the meter toindicate any response to the charging potential indicates an opencondenser or a condenser of a capacity too low to accommodate adiscernible charge with the applied potential. A short-circuitedcondenser is indicated by a reading on the meter of the full voltage ofthe direct current power supply.

Capacity measurements Because of the possibility of blowing the l-amperefuse i12, located beneaththe analyzer panel, when attempting to measurethe capacity of a short-circuited condenser, it is recommended thatevery condenser be subjected to the leakage test outlined in thepreceding paragraph before undertaking a measurement of the capacity.Having a 11G-volt {S0-cycle power supply available, capacity readingsare obtained by making the following connections. One side ofthe powersupply system is connected to the pin jack 11i. The other side of thepower supply system is connected to one side of the condenser undertest. The other side of the condenser is connected by means of aconductor to the 12.5 mid. pin jack 16. A reading of the capacity isobtained on the |25 scale of the meter upon the depression of thecapacity switch |10 (Figs. 1, 2, and 5) and the closing of contacts 113.1I" the meter reading is less than 12.5 on the 125 scale of the meter,the condenser connection is shifted to pin jack 115. If the meter stillreads less than 12.5 on the 125 scale, the connection from the condenseris shifted to the 0.125 mfd. terminal |14. When pin jack 116 is availedof, the reading of the l25 scaleof-the meter should be divided by 10 toobtain the proper mid. indication; when the pin jack 15 is used, thereading should be divided vby 100; and, when using the pin jack iM, thereading should be divided by 1,000. Resistances |11, 118, and 19 aredesigned for a denite frequency and, when the alternating currentpowersupply has a frequency other than 60 cycles, these resistances aremodied accordingly. These variations in the resistance's for differentfrequencies aretabulated in the table below. s.

Ftequem Resistance in ohms cy in cycles per Resistor Resistor Resistorsecond 179 178 177 Output measurements The six alternating currentvoltage measuring ranges are ideally suitable for output measurements.The blocking capacitor C1 isolates the output signals from the platepotentials applied to the power tubes. The desired range of thevoltmeter may be connected between the power tube plate terminal and thecathode or lament of the tube or the chassis of the radio without theuse of output adapters. Also, the meter m'ay be connected across thevoice coil terminals for outiput measurements during the usual radioreadjustment operations. The output measurements are taken by insertingthe analyzing plug P in the place of the power output tube and placingthe tube in the proper socket on the analyzer panel. The switch I4 isset to its A. C. V.-Mfds. position. The common volt terminal 42 isconnected to one of the pin jacks 534 or 55, depending upon the type oicathode in the power tube. A test lead is connected from the pin jack 43of the proper range, for instance 250, to one of the plate pin jacks,such as 52. The meter'nowindicates the output of signals impressed uponthe radio receiver and the latter should be Yadjusted for maximumdeflection. By the use of an oscillator for testing purposes, the outputof which is modulated by the frequency of the power source,

it has been found advantageous to note the actual readings of variousreceivers for useas comparisons and references in future adjustments.The output measurements of a radio receiver having the energy of a60-cycle, 100% modulated oscillator imposed thereon, provide an idealmethod for testing tubes. The tubes are tested by observing the eiect onthe output meter readings resulting from the replacement of questionabletubes with new tubes. Tubes tested in this manner are usually designatedas set tested tubes. This method of testing is also ideal for detecting`fading conditions within the receiver or tubes.

In view of the fact that any of the analytical circuits, except thefilament or heater circuits, numbered 3 and 4, may be broken by depressing the push button switches, 10, 1I, 12'l 15, and 16, it ispossible to connect numerous other devices suchV as head-phones, loudspeakers, phonograph pick-up devices, transformers, etc., for testingpurposes. the connections bythe switchboard arrangement of the analyzerpanel renders the tester disclosed herein capable of many uses forpresent needs as well as future ones.

It is understood that the expressions direct currents and alternatingcurrents appearingV in the specication and claims, are used in their Ygeneric sense and have reference to both voltageV The possibility ofvarying Y Y and current units, unless specifically stated other-v` Wise.,Y

Having described my invention, I claim:-

- l. In a portable radio testing apparatus, a single indicating meterfor indicating thereon direct current V voltages' and currents,alternatingV current voltages, capacities, andV resistance values,current elements comprising resistors and capacitors associated withsaid meter, and switch.

ing means for selecting said meter and appurte- Y nant circuit elementsfor operation to efect said indications. Y

2. In a ,portable radio testing apparatus, a single instrument having auniformly divided scale for indicating thereon a plurality of ranges ingcurrent voltages, and capacities,VV circuit ele-V ments comprisingresistors and capacitors Y associated with said instrument, andswitching means for` selecting said instrument "andV appurtenant circuitelements'foroperation to effect said indications. Y Y k i Y3. InV aportablerradio testing apparatus', a single instrument having auniformlyV divided scale for indicating'thereon a plurality ofranges ofdirect current voltages and currents, alternating current voltages, andcapacitiesfand a'second scale on said instrument calibrated in ohms,circuit Velements comprising resistors Y and capacitors Vassociated withsaidjm'eter, Yand switching means4 for selecting said instrument andappurtenant circuit elements f or operation to efect said indications.AY t Y .4. InV a testing apparatus, a direct current measuringinstrument, a uniform Vscale on said instrument forV indicatingalternating Vcurrent and direct current values thereon, Ya rectifier forY Yrectifying alternating currents to be measured by said instrument,acondenser in series with said rectifier, the combined impedance of saidseriescircuit bearingV a definite relation -to the resistance of the'circuit containing said measuring instrument when direct currentsaremeas-V ured, `corresponding to the Y formj factor of Vthe measuredalternating currents. Y

5. In a testing apparatus, a direct current measuring instrument'forindicating alternating Y the impedance of said first-mentionedcircuitbe-Y,

currentV and direct current values thereon, a rectifier for rectifyingalternating currents toV be measured by said instrument, a condenser inseries with said rectifier, aresistance in series .with said instrument,switching'm'eans for connecting al- VVternating current to be measuredin circuit with saidrectifier and condenser and direct current incircuit Vvvitlisaid instrument andresistance,

ingless than the resistance of said'second Ycircuit and bearingthe ratioof the form factor of the alternating current whereby the average valuesof ,the impressed alternating current obtained Vat the output Vof saidrectifier are indicated as root 1 mean square values on theV sameVVpoint ofthe uniform scaleas the average or effective values of directcurrent. j 1 Y Y 6.V lThe combination claimed in claim-4 wherein thereactance of said condenser YYforms the' V principal portion of Ysaidimpedance. Y

'7. The Ycombination claimed Vin claim 5 where? f in the reactantee ofsaid condenser Vconstitutes theV Y principal portion of said impedancewhereby va-V in the resistance of said rectifier are minimized.V A metercomprising a rectifier, a DArson-V riationsY in the indications arisingfrom changes Val salvanometerinstrumentfor measuring the output of saidrectifier, means for selectively conf necting said instrument to saidrectifier for measuring alternating currents and.V for disconnecnng andVinstrument fromsaid rectifierror Y measuring direct currents, impedanceVmeans formed, at least in part-of capacitivereactance in series withsaid rectifier upon 'the'measuring' ,of alternating currents forcontrolling thermaxi- Y mum'defiection ofthe needle of said galvanom- Yeter instrument. resistance means comprising a resistance in' serieswith said instrumentl'upon the measuring of directVV current, forcmitrolling the maximum defiection of the needle thereof, saidlast-mentioned Vresistance means beingv greaterthan said Vimpedancemeans correspond-V ing to the form factor of the measured alternate ingcurrents whereby the effective value of both f direct and alternatingcurrentsY is indicated by equal deflections ofthe needle of theinstrument.,v j 2o:I

9. A meter comprising a rectifier, r'a DArsonval galvanometer instrumentfor measuringY the Y output Yof said rectifier, means Vfor selectivelycon.V

necting said instrumentY to saidrectifier for measuring alternatingcurrent potentials andfor disconnecting said instrument from saidrectifier 25V Vfor measuring direct current potentials, impedance meansformed, atleast in part, of capacitive i reactance in series With'said,rectifierV upon vthe measuring of alternating current'potentials for 1controlling the maximum deflection of the needle of said galvanometerinstrument at thelowest range of operation'of said meter, resistancemeans comprising a resistance inseries with saidV instrument upon themeasuring Aoi' direct current potentials, for controlling the maximumde,-V

fiection ofV the needle thereof at the lowest rangev resistance meansbeing greater than said imped" ance means corresponding to the formVfactor of the measured alternating current potentials Ywhereby theAeffective, value of both direct and` alternating currentstis indicatedby equal deflec-k tions of the needle of the instrument at'thelowestrange of operation of said meter, at least one multiplier resistance forincreasing the range of of operation Yof said meter, saidlast-mentionedV said meter for indicating high directvcurrent po-ftentialsr, and a condenser in shunt with said mul- Ytiplier resistor fordecreasing the impedance v thereof upon the measuring ,ofV alternatingcurrent potentials to compensate for the form Vfactor thereof.

10. A meter comprising a rectifier, a DAr'sonf j val galvanometerinstrument for measuringtheoutput of said rectifier, means forselectively connecting -said instrument to said rectifierfor measuringalternating current potentials and forV :vr disconnecting saidinstrument from said rectifier Y for measuring direct currentpotentials, imped# Vance'means formed, at least in part, of'capacitivevreactance in series with said rectifier .upon the` measuring ofalternating currentpotentials for controlling the maximum deflection ofthe nee- Y dle of said galvanometer instrument at the lowest rangeofoperation ofvv said'r meter,.resistance means comprising a resistance inseries with said instrument upon the measuring offdirect currentpotentials, Vfor controlling the maximum defiection of the needleYthereof atfthe lowest range of the measured alternating currentpotentials whereby the effective value of both direct and alternatingcurrents is indicated by equal defiections of the needle of theinstrument at the lowestoperation of said metensaid last-mentioned Vre-ro sistance means being greater than said impedance means correspondingto the form factorof .t l

range of operation of said meter, a plurality of multiplier resistorsfor obtainingV higher operating ranges of' said meter forindicatinghigher direct current potentials, andy condensers in shuntwith said multiplier resistors for decreasing the impedance thereof uponlthe measuring of alternating current potentials to compensate for theform factor thereof.

11. A meter comprising a rectifier, a DArsonval galvanometer instrumentfor measuring the output of said rectier, means for selectivelyconnecting said instrument to said rectifier for measuring alternatingcurrent potentials and for disconnecting said instrument from saidrectifier for measuring direct current potentials, impedance meansformed primarilyV by a preponderance of capacitive reactance in serieswith said rectifier upon the measuring of alternating current potentialsfor controlling the maximum deflection of the needle of saidgalvanometer instrument at the lowest range of operation of said meter,resistance means' comprising a resistance in series with said instrumentupon the measuring of direct current potentials, for controlling themaximum deilection of the needle thereof at the lowest range ofoperation of said meter, said last-mentioned resistance means beinggreater than said impedance means corresponding to the form factor ofthe measured alternating current potentials whereby the eiective valueof both direct and alternating currents is indicated by equaldeflections of the needle of the instrument.

12. In a portable testing apparatus, an indicating meter, a socket insaid apparatus for receiving a tube having a plurality of electrodescomprising an electron emitting cathode, a grid and a plate, a pluralityof tube terminals associated with said socket, a set of terminals insaid apparatus connected to said tube terminals, a second set ofterminals corresponding to the last-mentioned terminals, a plurality ofconductors extending from said last-mentioned terminals, an analyzingplug having prongs adapted to fit into the tube socket in a radioapparatus, said prongs being connected to the ends of said conductors,connections in said testing apparatus between corresponding terminals ofsaid two sets of terminals, and switch means associated with saidconnections to break said normally closed connections to insert saidindicating meter in a lead between a prong in the analyzing plug and aterminal of the tube socket in said testing apparatus.

13. In a portable testing apparatus, an indicating meter, a plurality ofmeter terminals, comprising a common terminal, in said apparatus forconnecting said meter for operation for a plurality of ranges, a socketin said apparatus for receiving a tube having a plurality of electrodescomprising an electron emitting cathode, a grid and a plate, a pluralityof tube terminals associated with said socket, a set of terminals insaid apparatus connected to said tube terminals, a second set ofterminals corresponding to the last-mentioned terminals, a plurality ofconductors extending from said last-mentioned terminals, an analyzingplug having prongs adapted to t into the tube socket in a radioapparatus, said prongs being connected to the ends of said conductors,connections in said testing apparatus between corresponding terminals ofsaid two sets of terminals, a detachable conductor for connecting oneterminal of one of said sets of terminals with the common meterterminal, a second detachable conductor for connecting the terminal ofthe second set corresponding to said last-mentioned terminal to one ofthe other meter terminals, and switch means associated with saidconnections to 'break said normally'closed connections and to insertsaid indicating meter through said detachable conductors in a leadbetween a prong in the analyzing plug and a terminal of the tube socketin said testing apparatus.

14. In a portable testing apparatus, an indicating meter, terminals forsaid meter, a selfcontained battery in said apparatus, terminals for thepoles of said battery, a socket in said apparatus for receiving a tubehaving a plurality of electrodes comprising an electron emittingcathode, a control grid, and a plate, a plurality of tube terminalsassociated 'with said" socket, a set of terminals in saidv apparatusvconnected to said tube terminals, a second set of terminalscorresponding to said last-mentioned terminals, a plurality ofconductors extending Vfrom said last-mentioned terminals, an analyzingplug having prongs adaptedto t into'the tube socket in a radioapparatus, said prongs being connected to the ends of said conductors,connections in said testing apparatus between corresponding terminals oisaid two sets of terminals, detachable conductors connected between thebattery terminals and to the terminal of each set corresponding to thecontrol grid of the tube, detachable conductors connected between themeter terminals and the terminal of each set corresponding to the plateof the tube, and switch means associated with said connections to breaksaid normally closed connections to insert said battery in the lead fromthe prong in the analyzing plug corresponding to the grid and to insertsaid meter in the lead from the plate to note the effect of a differentpotential on theV grid of the tube upon the plate current.

15. In a portable testing apparatus, an indicating meter, a battery, asocket in said apparatus for receiving a tube having a plurality ofelectrodes, a plurality of tube terminals associated with said socketadapted to make electrical connection with the electrodes of the tube, aset of terminals in said apparatus connected to a plurality of said tubeterminals, a second set of terminals corresponding to saidlast-mentioned terminals normally conductively connected with therespective terminals of the rst set, a plurality of conductors extendingfrom said second set of terminals, an analyzing plug having connectorsadapted to make electrical contact with the terminals associated with atube socket in a radio apparatus, said connectors being joined to theends of said conductors, means operatively associated with saidconductively connected sets of terminals to break said normal conductiveconnection between one pair of terminals of the respective sets and toinsert said battery in a lead between a connector in said analyzing plugand a tube terminal of the tube socket in said testing apparatus, and asecond means operatively associated with said conductively connectedsets of terminals to break said normal conductive connection between asecond pair of terminals of the respective sets and to insert saidindicating meter in another lead between another connector in saidanalyzing plug and another tube terminal of the tube socket in saidtesting apparatus for indicating the change eiected by the insertion ofsaid battery.

16. In a portable testing apparatus, an indieating meter, a battery, asocket in said apparaitusjrfor receiving atubezhavina aypluraltyo!electrodes, apiurality of Atzu-beterminals,associateld Y withsaidsocket. adapted kte make electrical-cmnection 'with thefeieoirodes .ofthe tuinen.. :set `of.

, terminals'in saidmiparatusv connected tc a plu- VVraiity ofsaid tubetermina1s,;.fa Ysecond :set ci?VV f i terminals correspondingVto':saidlastmentioned terminals. .normally Y conductively .connectedwith the'respeciiive terminals vofthe first gset, ajplu-V rajity ofconductors extending from said second .of temnina1s',an analyzingplugiha'vingconf, Y

theternina-ls .aociated with a tube socket .in a

radio 'sappia.rais,r said connectorsbein'g joinedV Ato the Yends of'said conductors, yswitchV means opminal of the ftuhe socket` inrsaidtesting apparatus,

and'asecond switch means operatively associated *Y Y Y amianto! Y e Y Ye witnfsaid eonduetiveiymnneeted sets of temmen Lto .interruptselectively V'said normal conductive connection :between 1a, secondpairof terminalsoi` Y the respective'setsqand simultaneously V to insertY saidV indicating Jrxietcrl'in ,.'anotherlead Abetween i Y calsicther`.connector in j said analyzing;V plug *and anotherV tube terminal of thetube socket in'aaid Y Y testing `apparatus for indicating the f change iVeectedbythe insertion ofsaid battery.V Y

17.1In'1a metering circuit, arectin'er, a DArso'n` val gaivanometer formeasuring the output of said Y V f rectier, mean-s `for selectivelylconnecting said 1 galvanometer to ,the Youtnutcf said rectifieriformeasuring, alternatingV currents applledjto the -in`v put of saidrecti-ersandfor connecting saidiinstmment directly wlthadirect currentcircuit for Y Y measuring direct currents, arcondenser ,in series f withsaid rectifier, thefeombinedimpedancecfi Ysaid series circuitbearingaldenite re1aticnto the resistance of therneasuring circuit when'die rect currents are measured; correspondingV to the f *form factonofthe'nieasured alternating currents, Y

FLOYD FAUSE'I'I.

